Intraspecific Variation in Growth and Reproduction in Latitudinally Differentiated Populations of the Giant ScallopPlacopecten magellanicus(Gmelin)

The giant scallop, Placopecten magellanicus, exhibits a discrete gametogenic cycle which varies between populations. In our study, spawning occurred later in scallops from New Jersey than in those from Newfoundland, but there is no latitudinal trend when data from the literature are considered. Reproduction is probably controlled by local environmental factors.There was high intraspecific variation in shell and somatic growth rates, and in the production of somatic and germinal tissue. Reproductive output in particular showed great plasticity. Variation in these traits along a depth gradient on a micro-geographical scale was equal to or greater than variation on a latitudinal scale, although reproductive output in New Jersey scallops exceeded that of scallops from Newfoundland. Enhanced reproductive output was associated with reduced longevity.